Magnetic reed type ultrasensitive circuit breaker



R. w. HOEPPEL 3,227,838

MAGNETIC REED TYPE ULTRASENSITIVE CIRCUIT BREAKER Jan. 4, 1966 Filed Aug. 14. 1961 PVC. 5

M/VENTOQ United States Patent 3,227,838 MAGNETIC REED TYPE ULTRASENSITIVE CIRCUIT BREAKER Raymond W. Hoeppel, P20. Box 5, Oak View, Calif. Filed Aug. 14, 1%1, Ser. No. 131,383 3 Claims. (Cl. 200-87) This invention relates to method and systems for operation and construction of electromechanical circuit breakers, and more particularly to ultrasensitive electromechanical circuit breakers.

Ultrasensitive circuit breakers are normally complex in construction, prone to shock damage, incapable of handling appreciable currents at their contacts, subject to erratic operation under conditions of vibration and are sluggish in action.

An object of this invention is to provide a simple circuit breaker that responds to a very low wattage input and handles a moderately heavy load.

Another object is to provide a supersensitive circuit breaker that is very rugged with respect to shock and that can withstand appreciable vibration without operating erratically, and which is unaffected by changes in position.

Another object is to provide a circuit breaker whose electrical parts can be hermetically sealed.

Another object is to provide a circuit breaker that has long life with respect to both mechanical and electrical components.

With these objects in view, the purpose of this invention is accomplished by utilizing a magnetic reed switch located within a solenoid, with provision to establish a permanent uniform magnetic flux at said switch, which is opposite in polarity to that produced by the solenoid, by means of a permanent magnet remotely located in such position that it will just hold the switch closed when no current flows in the solenoid.

In embodiments of this invention provision is made for resetting the circuit breaker either electrically, by means of a momentary strong current through the solenoid, or mechanically, by movement of the magnet closer to the switch. Also provision is made for the adjustment of the sensitivity of the circuit breaker by means of a mechanical adjustment which varies the flux of the permanent magnet at the reed switch. Other features of the invention consist of certain novel methods of construction and modes of operation hereinafter described and defined in the claims.

In the accompanying drawing, FIGURE 1 shows a cross sectional elevation view through the center of a circuit breaker having manual reset and sensitivity control. FIGURE 2 shows a similar view of a similar circuit breaker constructed in cartridge form. FIGURE 3 shows a schematic circuit of a means for electrically resetting any of the above circuit breakers.

In every instance, the magnetic reed switch serves as the output control for the circuit breaker. Such reed switches consist of two overlapping, separated, magnetizable reeds which serves as armatures and contact points combined, and which are often hermetically sealed in an inert gas atmosphere. When the switch is in the vicinity of a magnetic field that is strong enough the reeds are suddenly attracted towards one another, closing the switch. The closed contacts will then remain closed even though the mngaetic flux is greatly diminished, but will open eventually as the field is still further diminished.

These switches have an unusually long life and will easily carry currents of two amperes or more, depending upon the type of contacts and the size of the switch. Because these reeds are biased magnetically when actuated, they are not as subject to erratic action under vibration as where spring biasing is used. Because of the low mo- "ice ment of inertia of the reeds and because they are fairly stiff, they can withstand severe shock without damage.

In order to obtain great sensitivity in the circuit breaker, described herein, it is necessary to first close the magnetic reed switch by increasing the magnetic flux in its vicinity and then this flux must be decreased until the switch is on the verge of opening, which flux is much less than that needed to close the switch. At this point, a very small reverse flux produced by passing a very small current of the proper polarity through the solenoid will rapidly open the reed switch, breaking the circuit. Thus the circuit breaker is polarity sensitive when it is actuated by direct current. However, it also can be actuated by a very small alternating current provided the frequency of the current is not greater than approximately 400 cycles, inasmuch as most reed switches can be closed by a pulse of 1 millisecond duration.

The circuit breaker can be made to respond to power inputs as low as microwatts or lower, which is within the range of sensitivity of the much more complex and fragile meter relays. In fact the magnetic reed circuit breaker can be used effectively to protect delicate electric meter windings, by installing the breaker in the meter circuit so that it breaks the circuits on overloads.

In FIGURE 1 is shown a complete circuit breaker in center cross section elevation view. Here a solenoid 2 is wound around a magnetic reed switch 1 which assembly is mounted on a non-magnetic support frame, by means of epoxy cement or other fastener. A push rod 5 to which is attached a permanent magnet 4 with one pole downward is spring biased upward via a non-magnetic spring 6, so that the magnet stays in one fixed position, with movement upward restricted by an adjustable thumb screw 7. Tapped holes 8 and 9 serve as fasteners to aid installation of the circuit breaker on a panel. If desired, a horseshoe magnet may be substituted for the bar magnet shown.

In operation the push rod 5 is momentarily pushed downward, thus lessening the distance between the magnet .and the switch, and closing, or reseting, the switch by the increased flux. The final distance between the magnet and the switch is then adjusted by means of thrurnbscrew 7 so that the switch still remains closed when the push lever is in its uppermost position. If this screw is moved too far upward the switch will open due to the lessened fiux, as the push lever moves upward. Maximum sensitivity of the switch is at that adjustment of screw 7 where the switch is on the verge of opening, but still remains closed when the push lever is released. Thus raising screw 7 increases the sensitivity. After setting the circuit breaker, the passage of a very small amount of direct current through the solenoid in such direction as to counteract the flux of the permanent magnet at the switch, will then cause the switch to open. If the circuit breaker is adjusted to a less sensitive setting, it may be reset with alternating current.

In FIGURE 2 is shown another type of construction for the circuit breaker, which is more enclosed. Here a solenoid 11 is wound around a magnetic reed switch 10 and this assembly is permanently mounted in the lower chamber of a cylinder 12 which is made of non-magnetic material, a non-magnetic partition 13 serves to separate the two chambers. The purpose of partition 13 is not necessarily to separate the cylinder into two sections, but rather to serve as a shoulder to restrict the movement of spring 16. If the entire switch-solenoid assembly is potted in plastic, or if a shoulder is added, this partition may be omitted as the spring is then restricted by the plastic or the shoulder. A permanent magnet 14, preferably a round shaped ceramic disc magnet, with one pole downward, is attached to a push rod 15 which slides freely in an aperture in thumbscrew 17. A non-magnetic spring 16 holds the magnet up against the lower surface of the thumb screw 17 during normal operation. A shoulder 19 and a nut 18 serve as panel fasteners for the assembly.

The operation of the circuit breaker shown in FIG- URE 2 is identical to that shown in FIGURE 1 and previously described, the push rod 15 being used to reset the breaker and the thumb screw 17 being used to adjust sensitivity.

As previously mentioned, either of these circuit breakers can be reset electrically, in which instance, the push lever may be omitted. Resetting electrically is accomplished by passing a heavy current through the solenoid momentarily, thus creating enough magnetic flux to close the reed switch. This is best accomplished by means of an external double throw switch as shown in FIGURE 3, wherein in one position the solenoid 20 is connected to a battery, or other source of voltage, to create the strong flux to reset the reed switch, and in the other position it is connected to the circuit to be controlled.

Even the single pole double throw switch may be eliminated if a second solenoid is placed in the vicinity of the reed switch, such solenoid being used only for resetting the circuit breaker, in which case a single pole single throw switch is required to momentarily energize and reset the solenoid.

For resetting, alternating current, or preferably direct current may be used, but where the breaker is set at maximum sensitivity, direct current may be necessary.

Where it is not desired to change the sensitivity, the thumb screw sensitivity adjustment may be omitted from the circuit breaker. If a sensitivity adjustment is not needed and if resetting is to be accomplished by electrical means, bot-h the push lever and the thumb screw sensitivity control may be omitted, in which instance the circuit breaker comprises only the solenoid-switch combination and the permanent magnet, which are held spaced at a given distance by a non-magnetic frame. In this latter instance, a single pole double throw push button switch is needed for the electrical resetting, which switch may be incorporated in the circuit breaker assembly.

Where stray magnetic fields are likely to be encountered, the entire circuit breaker assembly can be surrounded by magnetic flux shielding. Where vibration is excessive, the entire circuit breaker assembly can be shock mounted with respect to the panel.

What is claimed is:

1. A sensitive circuit breaker comprising in combination: a normally open magnetic reed switch; a solenoid surrounding said switch; a non-magnetic framework mounting said switch and solenoid; a permanent magnet moveably mounted to said framework in a position spaced from said switch and solenoid to define an air gap capable of variation by movement of said magnet, said magnet being in fiux coupling relationship to said switch through said air gap, and said flux being sufiicient to close said switch when said solenoid is de-energized; means for moving said magnet with respect to said switch to a given position to change said air gap and thereby to decrease said flux to a value just sufiicient to hold said switch closed when said solenoid is de-energized, so that a given current is required in said solenoid to open said switch; and stop means included in said framework defining said given position whereby said magnet may be consistently repositioned to said given position after any movement of said magnet.

2. A sensitive circuit breaker according to claim 1 including means for moving said stop means to change said given position to a new position and thereby to change said given current required in said solenoid to open said switch.

3. A sensitive circuit breaker according to claim 1 in which said means for moving said magnet to a position to decrease said flux at said switch comprises a spring mounted in said framework.

References Cited by the Examiner UNITED STATES PATENTS 2,283,340 5/1942 "Ray 200-87 2,298,068 10/1942 Pierce 200-87 2,877,315 3/1959 Oliver 200-87 2,902,558 9/1959 Peek 200-87 2,922,858 1/1960 Houser 200-87 2,999,558 9/1961 Pfleiderer et al. 200-87 3,012,116 12/1961 Boylan et al. 200-87 3,035,136 5/1962 Dal Bianco 200-87 3,046,370 7/ 1962 Adams et al 200-87 BERNARD A. GILHEANY, Primary Examiner. RICHARD M. WOOD, Examiner. 

1. A SENSITIVE CIRCUIT BREAKER COMPRISING IN COMBINATION: A NORMALLY OPEN MAGNETIC REED SWITCH; A SOLENOID SURROUNDING SAID SWITCH; A NON-MAGNETIC FRAMEWORK MOUNTING SAID SWITCH AND SOLENOID; A PERMANENT MAGNET MOVEABLY MOUNTED TO SAID FRAMEWORK IN A POSITION SPACED FROM SAID SWITCH AND SOLENOID TO DEFINE AN AIR GAP CAPABLE OF VARIATION BY MOVEMENT OF SAID MAGNET, SAID MAGNET BEING INF FLUX COUPLING RELATIONSHIP TO SAID SWITCH THROUGH SAID AIR GAP, AND SAID FLUX BEING SUFFICIENT TO CLOSE SAID SWITCH WHEN SAID SOLENOID IS DE-ENERGIZED; MEANS FOR MOVING SAID MAGNET WITH RESPECT TO SAID SWITCH TO A GIVEN POSITION TO CHANGE SAID AIR GAP AND THEREBY TO DECREASE SAID FLUX TO A VALUE JUST SUFFICIENT TO HOLD SAID SWITCH CLOSED WHEN SAID SOLENOID IS DE-ENERGIZED, SO THAT A GIVEN CURRENT IS REQUIRED IN SAID SOLENOID TO OPEN SAID SWITCH; AND STOP MEANS INCLUDED IN SAID FRAMEWORK DEFINING SAID GIVEN POSITION WHEREBY SAID MAGNET MAY BE CONSISTENTLY REPOSITIONED TO SAID GIVEN POSITION AFTER ANY MOVEMENT OF SAID MAGNET. 